The present invention relates to a scanning-type laser marking method and apparatus.
In the scanning-type laser marking method, a highly focused laser beam is projected onto a workpiece. The laser beam is swung by a scan mirror so that a beam spot of the laser scans a surface of the workpiece. A point on the workpiece surface where the laser beam spot hits is instantly metallurgically processed (melted, sublimated, discolored etc.,) by the laser beam energy. The laser beam scanning or drawing results in marking desired patterns, such as patterns of a character, figure or symbol, on the workpiece surface.
The laser marking method of scanning type has an advantage of non-contact marking of the workpiece. However, when a workpiece surface is dirtied or uneven, a mark pattern of poor quality, including broken or thinned portions, is formed.
In the prior art, an operator must pre-clean a surface of the workpiece, particularly a portion to be marked, if it has undesired impurities or unevenness. To this end, the operator uses cloth, tissue paper or the like, soaked in detergent or solvent such as acetone or ethanol, to wipe the workpiece surface, or uses a brush to scrub it.
A deeply etched pattern can be marked with higher energy of a laser beam. In such cases, metal particles or slag produced in the marking process remain in marked grooves, or burrs can be formed on groove edges. Since the results are unsatisfactory, the operator must post-clean the marked area and surrounding area by wiping or polishing.
The manual pre-cleaning and post-cleaning required in the prior art laser marking is, however, a painstaking labor on a part of an operator. In addition, filaments of a cloth or tissue paper may be caught in unevenness of a workpiece surface or burrs at the time of wiping or polishing. Sometimes, scratches may be formed on a workpiece surface (in particular, an area marked or to be marked) so that re-polishing is needed. Therefore, the prior art has problems of low productivity and difficult quality control.